Mechanical valve operators have heretofore been used on valves having rotatable valve shafts requiring relatively large amounts of torque for opening and closing the same. These types of valve operators have been particularly useful on butterfly valves wherein such valves include a butterfly valve plate or member carried by a rotatable valve shaft, the valve plate or member being pivoted between a closed position across the flow passage of the valve body to an opened position substantially parallel to the axis of the flow passage in the valve body. Large torques result in these types of butterfly valves, especially when the valves are large in size and/or used in systems where the fluid pressure is high and, thus, there is the necessity of providing a mechanical valve operator designed to provide a mechanical advantage to overcome the large torques. Many of these mechanical valve operators are either of the type driven by an electric drive means or by a mechanical means, such as a wrench or handle, the valve operators having in common means to produce a mechanical advantage capable of rotating the rotatable valve shafts requiring large torques for operation.
Other types of valves use mechanical valve operators wherein such valves have a rotatable valve shaft and the valves require large torques for operation of the shaft to open and close the valve. In this respect, mechanical valve operators have been used on large size ball valves, plug valves, and even gate valves wherein reciprocation of the gate member is accomplished by rotary movement of a shaft.
Valve operators or operating mechanisms for attachment to valves having a rotatable valve shaft usually include a housing, an operating shaft journaled in the housing, the operating shaft having a screw thread thereon, and a follower or operator nut carried on the screw thread and movable between limits longitudinal of the operating shaft. The follower is operatively connected to the rotatable valve shaft of a valve member by a pivotal lever or bellcrank member, or the like, and when the follower moves on the operating shaft, the lever pivots causing the rotatable valve shaft to rotate between certain limits. Usually, the lever or bellcrank member is in the form of a bifurcated yoke member pivotally connected to the rotatable valve shaft, the bifurcated yoke member receiving the following member between its arm and having slots in its arms for receiving projecting pin members from follower members.
In prior art, the valve operators were provided with spaced stop means to limit the travel of the follower member or operating nut and, thus, limit the amount of rotation of the valve shaft to control the movement of the valve member attached to the shaft between an opened and closed position. Some of these prior valve operators had complicated means for adjusting the stop which controlled the position of the valve member in the closed position, whereas other of the valve operators had separate means to adjust the stops for both controlling the valve member in its opened and closed positions. The adjustment means of the prior art was usually quite complicated to operate, and if adjustment were made in the wrong direction, the procedure of adjustment had to be repeated over and over before a final position of the stops was obtained.
So far as known, none of the prior art valve operators utilizing stops for controlling the amount of movement of the valve member had means whereby both stops were simultaneously adjusted in the same direction so as to maintain a predetermined amount of movement between the valve closed and valve opened positions of the valve member. For example, in butterfly valves, the valve operator for such valves is initially installed on the butterfly valve and the adjustment of stops is made so that the butterfly valve member or disk completely seals against the seat and opens a predetermined distance, usually 90.degree., so as to be substantially parallel with the flow passage through the valve. Once this initial setting has been made and the butterfly valve is operated over a period of time, the valve seat for the disk might become worn and the valve might leak when in the closed position. This necessitates readjustment of the disk or butterfly valve member to seat properly and usually this adjustment is slight, but it does not affect the overall amount of movement of the valve member unless the valve open stop is also adjusted. In the prior art, this had to be done by a separate adjustment of the stop for limiting the movement of the follower nut in a direction for moving the valve member in opened position and this was difficult to obtain an accurate setting without complete disassembly of the valve operator.
The prior art valve operators were usually designed to be attached to a particular size valve having a particular size valve operating stem. In such situations where a valve operator was made for only one particular size valve operating stem or shaft, the manufacturer did not have too much flexibility in operation because the manufacturer had to have on supply a number of separate valve operators or mechanisms for each particular size of valve.
Prior art arrangements relating to valve operators or operating mechanisms are disclosed in the following U.S. Pat. Nos.
2,930,252 Sears et al. Mar. 29, 1960;
3,420,500 Geiselman, Jan. 7, 1969;
3,452,766 Fenster, July 1, 1969;
3,459,058 Fawkes, Aug. 5, 1969;
3,575,378 Fawkes, Apr. 20, 1971.
While some of the above-listed patents disclose adjustments for valve operators or operating mechanisms none of the patents suggest a solution to the problem where the adjustment of the valve member of a valve having a rotatable valve shaft can be made for the valve closed position without affecting the amount of overall movement of the valve member unless separate adjustment means are provided to further control the valve opened position after adjustment of the closed position. Further, none of the above patents suggest a simplified solution to the problem of making a valve operator or operating mechanism which is capable of use with various size valves having various size rotatable valve shafts.